The present invention relates to a transformer apparatus with rectifiers, and more particularly to a transformer apparatus comprising two or more transformers which have terminal plates connected through rectifiers to the opposite ends of the secondary windings thereof and center tap terminal plates extending from intermediate portions of the secondary windings.
There has been known a transformer apparatus having a pair of terminal plates connected through rectifiers to the opposite ends of the secondary winding of a transformer. The transformer apparatus of this design is mostly incorporated in a resistance welding system. More specifically, the first terminal plate is disposed on one side of the transformer and the second terminal plate is disposed on the other side of the transformer. These terminal plates are coupled to ends of first and second conductive bodies, respectively, the other ends of which are connected to the welding gun of the resistance welding system.
A resistance welding apparatus of the inverter type includes switching devices, such as power transistors, on the primary side. Because of the capacity of these power transistors or the capacity of diodes on the secondary side, there is a certain limitation on a welding current that can be supplied to the welding gun. In some applications which require a relatively large welding current to weld thick plates or plated steel plates, for example, it is desirable to connect a plurality of transformers for a higher welding current capacity.
To meet such a demand with the known transformer apparatus, the first terminal plates of the connected transformers have to be connected together at one end of the first conductive body, and the second terminal plates of the connected transformers have to be connected together at one end of the second conductive body, with the other ends of the first and second conductive bodies extending closely to each other and being connected to the welding gun. With this arrangement, however, the first and second conductive bodies project out of the transformers, and the transformers are spaced a distance which is required to connect the terminal plates to the first and second conductive bodies. As a result, the transformer apparatus is large and heavy as a whole. Therefore, the resistance welding apparatus incorporating the transformer apparatus is also large and heavy. It is difficult to install the large and heavy resistance welding apparatus on the arm of a robot or the like for an automated welding operation.
Since the first and second conductive bodies to which the first and second terminal plates are connected are considerably long, they cause a substantial electric power loss which makes it impossible to supply a large electric current efficiently to the welding gun.